Bromus inermis

• Smooth Brome

Seed - sow spring in situ. The seedbed should be firm and seed should not be covered to more than 6 - 13 mm depth. Seed rates of 3.3 kilos per hectare are used when the plant is sown in a pure stand, though it is more often sown in a mixture with various legumes such as alfalfa, sweet clover, red clover or Lotus corniculatus^[1]. There are approximately 300,000 seeds per kilo^[1].

Best adapted to regions with moderate rainfall and moderate cool summer temperatures, it is suited to silt or clay soils and deep loams, but also does well on light sandy soils and on well-drained soils. Plants are less drought resistant than crested wheatgrass and they do not tolerate temperature extremes. Smooth brome is suited for irrigated areas but is not recommended for saline or alkali soils^[1]. Smooth brome is reported to tolerate an annual precipitation of 32 to 176cm, an annual average temperature range of 4.3 to 19.9°C and a pH in the range of 4.9 to 8.2^[1]. Smooth brome is also reported to tolerate alkali conditions, disease, drought, frost, fungi, grazing, mycobacterium, salt, viruses, and weeds^[1]..

There are a number of named varieties, selected mainly as hay and pasture crops. These cultivars are divided into two groups, northern and southern. The southern group is less cold-hardy and does not survive average winter conditions further north than southern Minnesota in N. America, the northern group is much more cold tolerant^[1].

The genus Bromus contains many complex, polyploid series. Bromus inermis belongs to section Bromopsis, containing wild species with chromosome numbers ranging from 2x to 8x. Following its introduction to North America, smooth broome, an aggressive species, has tended to replace native American species of sect. Bromopsis, especially B. pumpellianus. Hybridization studies have been made between: B. inermis, 8x; B. pumpellianus, 8x; and material of the introduced B. erectus complex (6x, 8x, 10x, though the last is probably itself hybrid). An objective of these studies was to incorporate into inermis the larger seeds of pumpellianus and better seedling vigour of erectus. The three species are related, crossable and give quite fertile hybrids. Collections of B. inermis in North America show varying meiotic irregularity and aneuploidy. This is probably a result of introgression from B. pumpellianus and the B. erectus complex. Quite a high degree of meiotic irregularity may be tolerated under natural conditions in a long lived, cross- pollinated species such as B. inermis, which can spread aggressively by rhizomes^[1].